This invention relates to a method of and an apparatus for longwall mining. More particularly this invention concerns an apparatus for supporting the roof of a mine while a longwall face cut into one wall of the mine is worked.
Longwall mining is normally used for the recovery of coal. In such a mining method a horizontal drift or mine extends along the seam to be worked. The roof of this mine is propped up with supports normally standing on legs at the mine walls, that is at the vertical sides of the mine or drift. In order to work the longwall face it is therefore necessary to remove the legs of the roof props at the working location.
Typically, this requires secondary struts to be braced between the part of the prop normally termed the arch that engages the mine roof, so as to allow the leg on one side to be removed. Such struts are usually complicated screw or hydraulic arrangements which must be manually and paintakingly emplaced one-by-one. Furthermore, the use of such secondary struts frequently results in damage to the arches so that subsequent remounting of the legs thereon proves rather difficult.
Not only must the roof arches be supported at locations spaced somewhat from the longwall face being worked in the side wall of the mine, but it is then necessary to move a considerable amount of equipment about in the mine in order to work the face. The use of a plurality of separate struts as described above greatly complicates maneuvering within the mine and even further slows down the longwall working of the face.